CFD-based erosion modelling of simple and complex geometries
Choke valves are important components in oil and gas production systems that are used to control the pressure and flowrate of fluids issuing from oil and gas reservoirs. The presence of sand in the production fluids can cause considerable damage to such components, and as sand is increasingly becoming an issue in oil and gas production, valve manufacturers need to find ways of reducing their product's susceptibility to solid particle erosion. A CFD-based erosion modelling tool is achieved by first solving the fluid flow through the component of interest; tracking particles through the fluid and extracting impact data on all solid surfaces; and finally relating the particle impact data to erosive wear through a semi-empirical equation. The present study has focussed on the development and validation of a CFD-based erosion modelling method for simple and complex geometries. Erosion testing has been carried out on a range of choke valve materials to provide the fundamental data required in constructing equations that relate erosion rate to particle impact velocity and angle. These equations have in turn been implemented in a commercial CFD code to provide the complete erosion modelling solution. Validation of the method has been effected by comparing predicted results to experimental test data for both simple and complex geometries. Both single phase and abrasive flows have been considered in comparisons. For the simple geometries, reasonable agreement was obtained between predicted and measured pressure drop for the simplest cases, but predicted mass loss was considerably less than the measured amount. With the complex geometries (Multi-Orifice Sleeve choke valves), good agreement for pressure drop was obtained for some valve positions, but not so good for others. Significant differences were observed in mass loss predictions for the complex geometries, which raise questions as to the usefulness of CFD-based methods for predicting component lifetime.